1. Field of the Invention
The present invention relates to a continuously variable transmission used for general industrial machineries, vehicles, electric motors and so on, and particularly to a variable transmission for controlling a variable torque while distinguishing and supplying the elastic force and the pressing force to a pulley and performing the friction force stabilization and the high efficient transmission.
2. Related Art
The motion of a fixed horse power type belt continuously variable transmission has been developed in U.S. Pat. Nos. 4,973,288, 5,269,726 and the like, but satisfactory products have not been realized. Both the patents have an idea that in the former, input and output pulleys are simultaneously pressed by oil pressure and in the latter, by screw winding up. However, these ideas have decisive and important or principle defects. Normally, the output horse power P [W] which is transmitted by an output pulley to a load is determined by a relation formula P=1.027xc3x97Nxc3x97T between the rotating speed N [rpm] and the torque T [Kgm]. The rotating speed is decided by a contact position between a belt and a pulley, that is, a radius ratio, while the torque is decided by a contact friction pressure therebetween. This means that the rotating speed is determined merely by the positioning control of the belt in the pulley, while the shaft torque is always determined merely by the friction pressure control of the pulley. Accordingly, with respect to the securing measures for the desired rotating speed and torque in the continuously variable transmission, the aforementioned relation equation itself shows that the variable pitch positioning control and the friction pressure control are distinguished and applied to the pulleys and synchronously operated mutually. However, in the ideas of the above-described U.P. patents, even if the positioning function by a supply of pressing force should be applied synchronously to the input and output pulleys, there is no assurance of always maintaining a proper belt position, and not to mention, the torque assurance function for always applying the desired friction force to both the pulleys is not present at all in the transmitting system. This indicates that in the ideas of the aforesaid patents, secureness and maintenance of proper rotating speed and torque can not be accomplished, and the desired horse power transmission is impossible in terms of principle.
On the other hand, the present applicant has proposed, in EP Application publication No. EP 0931960A2, separation of roles for functions of the pressing control and the positioning control to two input and output pulleys. However, some unsolved problems still remain. The first problem is that the friction force between the belt and the pulley is instable, and the second problem is that the transmission efficiency is deteriorated. The former disables the transmission in the low speed area of a tension type belt. The cause is that in the friction force securing measures by the external pressing to the pulley directly, when the contact radius or area increases, the friction coefficient of the transmission surface becomes instable to bring forth the surplus friction force. In the latter, even a compression type belt, the transmission efficiency is maximum at and in the vicinity of the speed ratio xcex5=1 but in the other speed ratio areas, the contact area of both the pulleys is unbalanced and the efficiency is worsened therein. That is, the cause is supposed to result from the simultaneous generation of heat generation caused by the moving-in or rolling-in of the belt due to the surplus friction force on the side where the contact area in both the pulleys increases, and heat generation of a slip due to the short of friction force on the side where the contact area reduces.
It is a common object of the present invention to provide a continuously variable transmission particularly suitable for a constant horse power type in which when the friction force between a variable pitch pulley V-groove and a V-belt is controlled by a supply of external pressing force of an operating unit, the friction force of the other pulley is controlled by a supply of external elastic force in order to secure a shaft torque of one pulley out of input and output pulleys, the shaft torque of said one pulley is indirectly adjusted via a belt tension, not being restricted by the kind of belts.
It is a first object of the present invention to provide an arrangement wherein particularly in order to secure a torque of an output pulley, a controlling device compensates for a short of the friction force of an input pulley, always supplies the elastic force to the input pulleys to variably control the friction force of the input pulley, and to indirectly perform variable torque control the output pulley via a belt tension.
It is a second object of the present invention to provide an arrangement wherein in order to avoid rolling-in of a belt caused by direct pressing to an output pulley to stably secure the output friction force, a controlling device variably press-controls a pressing value for always supplying the elastic force to an input pulley, indirectly makes use of a wedge effect of an output pulley V-groove to control the output friction force and variably controls torque, whereby a constant horse power transmission is achieved with high efficiency and stableness in particularly a large ratio area without being restricted by the kinds of belts such as a tension type or a compression type.
It is a third object of the present invention to provide a continuously variable transmission which enlarges the whole variable speed area and has the optimum transmitting efficiency, wherein a short of the friction force of an input pulley and a surplus of the friction force of an output pulley in a large ratio area are suppressed, and also a surplus of the friction force of an input pulley and/or a short of the friction force of an output pulley in a small ratio area are suppressed.
It is a fourth object of the present invention to provide a continuously variable transmission performing the high efficient and stable transmission, wherein when said third object is embodied, an operating mechanism capable of distinguishing the pressing force and the elastic force and/or a simple pressing mechanism capable of distinguishing and supplying the pressing force and the elastic force are disposed on one of input and output pulleys and on the other, respectively.
It is a fifth object of the present invention to provide an operating mechanism capable of distinguishing and supplying, in response to respective instructions, the non-elastic pressing force for accurately positioning a pulley V-groove to a variable disk of one or both of an input pulley and an output pulley of a continuously variable transmission, and the elastic fore for settling the absorption of errors, impact vibrations or the like caused in the transmitting operation.
It is a sixth object of the present invention to provide a pressing mechanism, which is further simplified in said fifth object, capable of distinguishing and supplying, in response to a single control instruction, the non-elastic pressing force to a variable disk of one or both input and output pulleys simply and with light weight, and the elastic force of an elastic member.
The common object of the present invention is achieved by a continuously variable transmission, wherein in order to secure a torque of one pulley out of input and output pulleys for effecting the constant horse power transmission, an operating unit always supplies and controls the elastic force generated by compressing in series an elastic device by a compressing device to the other pulley and variably presses and controls said other pulley in response to an instruction of output rotating speed or speed ratio, and a controlling device controls the shaft torque of said one pulley indirectly via a belt by operation of the friction force of said other pulley to perform the variable torque control.
The first object of the present invention is achieved by an arrangement wherein an input operating unit, which comprises a pressing device for always supplying the elastic force generated by series-compressing an elastic device by a compressing device to an input pulley, and a driving source for effecting the variable pressing control via said pressing device according to an instruction of a controlling device, variably presses and controls the friction force of an input pulley to thereby indirectly variably torque-control the shaft torque of said output pulley via a belt.
The second object of the present invention is achieved by an arrangement wherein the follower function for always effecting variable press-control by a supply of the elastic force and the reference function for effecting variable positioning control substantially under non-pressure at the time of non-speed change motion and under pressure at the time of speed change motion are applied to an input pulley and an output pulley, respectively, and a controlling device indirectly variably torque-controls an output shaft by the wedge friction force formed from a V-belt and a V-groove of the output pulley from the friction force of the input pulley by an input operating unit via said V-belt.
The third object of the present invention is achieved by an arrangement wherein in a large ratio area of a continuously variable transmission, the follower function and the reference function are given to an input pulley and an output pulley, respectively, while in a small ratio area, the reference function and the follower function are given to the input pulley and the output pulley, respectively, and each operating unit or controlling device switches the operating functions of the respective pulleys halfway of the speed change area.
The fourth object of the present invention is achieved by an arrangement wherein one and the other of movable disks of input and output pulleys are pressed and switched by an individual operating unit in which two compressing devices individually series-connect an elastic device and a contact device, and by a distinguishing operating unit in which a single compressing device series-connects a parallel body comprising an elastic device and a contact device, respectively.
The fifth object of the present invention is achieved by an operating unit in which a first pressing device having an elastic device and a first compressing device superposed in series to one or both of movable disks of input and output pulleys and a second pressing device having a contact device and a second compressing device connected in series individually supply the elastic force and the pressing force, respectively.
The sixth object of the present invention is achieved by an operating unit in which a pressing device having an elastic device and a compressing device superposed in series and having a contact device and said elastic device connected in parallel, to one or both of movable disks of input and output pulleys, distinguishes and supplies a speed change area to an elastic force area and a pressing force area in response to a control instruction.
The idea of the present invention is not limited to a wet type in which both a variable speed transmission device and a variable speed control device are received in an oil pan, but a dry type in which both the devices are received in air or a dry type in which they are individually received may be applied. Further, the present invention may be applied particularly to a constant horse power transmission type transmission or a constant torque type transmission which exhibits a great effect. While for an operating unit of a variable speed control device, an individual pressing system comprising a first and a second pressing device in distinguishing the pressing force and the elastic force, and a composite pressing system using a composite device have been disclosed, it is to be noted that both input and output operating units may be of an individual pressing system, or an arrangement, in which an input side is of a composite pressing system and an output side is of an individual pressing system, may be employed. In this case, pre-pressure Pso shown in FIG. 6B need not always be applied to the output pulley. All of the pressing device for pressing a pulley, the composite device, the compressing device, the elastic device or the contact device are illustrated in the non-rotational arrangement, but they can be used in the rotational state, and the mounting position thereof is not restricted to the periphery of the pulley but they can be disposed in a suitable position by a pressure transmitting device of oil pressure or a lever.
While in switching the pressing force of an operating unit into the elastic force, an example of switching at the speed ratio speed xcex5=1 has been shown, it is to be noted that the switching can be done at a suitable speed ratio, and as the reference of the switching operation, the output rotating speed or the output torque may be employed instead of the speed ratio. In this case, preferably, both the output rotating speed and the torque are subjected to the momentary bumpless transfer. When the input power is changed in speed as in the internal combustion engine, the DC motor or the like, the continuously variable transmission remains at a certain constant speed ratio, and only the output torque may be applied with the variable pressing control by an input or output operating unit corresponding to the number of an input or output rotation. Since the pulley of the reference function performs the rotating speed control and that of the follower function performs the torque control, it is obvious that when the operating unit is switched in function, naturally, a control instruction supplied from the controlling device should be simultaneously switched, and said instruction should naturally be distinguished from a rotating speed instruction of a speed increase and a speed decrease, and a torque instruction of a pressure increase and a pressure decrease for the supply control. Accordingly, at the time of deterioration of a belt, the compensated rotating speed instruction and at the time of deterioration of an elastic member, the compensated torque instruction should be switched and supplied, respectively. It should be noticed that synchronous operation is a motion in which the number of rotation No is inversely proportional to or proportional to the output torque To and a constant-horsepower transmission and a constant torque transmission are synchronously associated with each other, while the asynchronous operation is a motion in which the number of rotation No and the torque To are not synchronously associated with each other. Therefore, the single variable control for only the follower pulley allows The control of the output shaft torque according to a variable speed input power. If the No and To are simultaneously decreased and then are stopped when the transmission stop instruction is supplied, the elastic member is free from deterioration caused by a high pressure during the stoppage and a low speed start-up is achieved at the time of next start for transmission.
Further, the substitution and common use of various devices, parts or the like can be variously changed. The pressing device is arbitrary in arrangement and order if the compressing device is connected in series with the elastic device and/or the contact device. The compressing device may be other winches, hydraulic jacks or the like if it can hold stably the pressing position after the stoppage of supplying a instruction signal. The elastic device may be any type without limited to the dish spring. The contact device may be also of other forms, for example, the elastic members themselves cause to have contact elements and are arranged in series. The pressing means such as slider elements, sliders, sliding materials or the like may be jointly used one another, or substituted for other members such as bodies, pulley disks, pressure transmitting devices or the like. The pressure transmitting device and the detector may be of any other types, and for example, the pressure transmitting device may transmit pressure within a hollow shaft of a pulley. While an example has been shown in which the control motors as a driving source are individually disposed every pressing device, it is noted that they can be used in common or simplified using a switching unit such as the well-known transmission or gear synchronous fitting device, and the motors may be of AC or a step motor. In the simultaneous pressing device of the movable disk and the elastic member, the operating amount of the compressing device may be constituted to be proportional or inversely proportional between relative distances of both disks and to be inversely proportional or proportional between the elastic forces of the elastic members, respectively.
The pressing device having the motor and the compressing device requires to withstand high pressure of pulleys, positioning with high accuracy for a long period, and supplying and controlling of pressure vales. Therefore, it is necessary in a pressurizing system to eliminate positively error signal factors to control instructions such as a self-locking function, that is, a reversing-impeding function and a motor overrun-impeding function. Accordingly, one direction transmission such as a metal surface contact friction means such as a trapezoidal screw or a worm transmission should be used, and a motor with a clutch, brake function or a reversing-impeding step motor should be applied. The sliding amount of the compressing device merely comprises the pulley moving portion lp in the reference function, but in the follower function, the elastic member compressing amount 1s is added, totaling to lp+ls in the moving amount. Accordingly, the rotating speed instruction and the torque instruction are different from each other in the operating amount as well as the operating direction, and in case of the winding-up sliding device, the known elements such as the winding-up pitch, rotational direction, thread-groove machined direction such as right thread and left thread, and ratio of the gear transmitter may be selected according to the design.
Various control forms of the controlling device 70 are considered. When the accuracy is not required in the output rotating speed N0 or the output torque T0, the operating amount initially set in advance may be supplied. When the high accuracy is maintained and the high speed response of the speed change motion is preferential, the circumferential length of a belt or the deteriorated error of the settling of an elastic member are periodically detected, the compensating amount is calculated and added so as to have a value determined in advance in a memory by CPU to instructions of the rotating speed or torque according to the deteriorated amount to impart them to operating units and servo control the detected value in an open loop without feeding it back. Further, where the high accurate control is required, the detected values are compared with a reference value determined in advance in a memory to supply a negative feedback control to input or output operating unit, thereby performing a long-term operation with extremely high efficiency.